The project is attempting to better characterize the pathophysiology of chronic orofacial pain through a series of clinical investigations. A clinical study in progress is evaluating the relationship between sleep disorders and temporomandibular disorders (TMD) which are thought to result in nocturnal muscle hyperactivity leading to pain in the muscles of mastication especially upon awakening. A double-blind crossover study is being conducted in which subjects receive either triazolam, a benzodiazepine hypnotic, or placebo over the course of five days with concurrent monitoring of pain and sleep architecture. Following a washout period of three days, subjects receive the alternative treatment and are monitored similarly. Documentation of an improvement in the quality and quantity of sleep by polysomnography and a parallel change in pain in the temporomandibular region is interpreted as evidence of a relationship between sleep disorders and orofacial pain. Interim data analysis suggests a functional relationship between alterations in sleep architecture, sleep quality, and pain in the muscles of mastication. A second study is investigating arthrocentesis of the temporomandibular joint (TMJ ) as a possible therapeutic modality and as a means to collect fluid and cells from the TMJ for later analyses. This study uses a randomized double-blind design to administer either a saline wash or an anesthetic agent to the TMJ and then to assess the effect on pain and mandibular range of motion. The arthrocentesis is performed with a novel coaxial needle technique developed by the primary investigator. Preliminary findings suggest a therapeutic benefit to a saline lavage of the TMJ and demonstrate the efficacy of the coaxial needle device in performing arthrocentesis in TMD patients. A third study involves an investigation of an auriculotemporal nerve block using either a local anesthetic or saline as a possible diagnostic procedure to assist in the determination of the source of facial pain in TMD patients. Using a randomized double-blind design, thirty-five patients with TMJ pain received an auriculotemporal nerve block with either lidocaine 2% or saline. Pain and range of motion measurements were collected both before and after the block. An interim analysis of data supports the use of an auriculotemporal nerve block as a diagnostic procedure in TMD patients and suggests that some of muscle pain perceived by these patients may be augmented by input from the TMJ. A fourth study involves an investigation of idiopathic jaw pain using single photon emission computed tomography (SPECT) to determine whether or not this pain might be the result of a neuralgia induced subacute osteomyelitis. Patients are clinically evaluated to eliminate any organic etiologic factors responsible for their pain. SPECT images of the head and neck are then obtained and subsequently evaluated by a nuclear medicine physician who is unaware of the location of patient's pain. The relationship between regions of radio-isotope uptake with the area of pain within the jaws is being evaluated. Preliminary findings in sixteen patients with idiopathic jaw pain lend tentative support to the hypothesis that idiopathic jaw pain is the result of a localized subacute osteomyelitis in some patients.